NEW YORK (AP) — Top-seeded Novak Djokovic was defaulted from his fourth-round match at the U.S. Open after he accidentally hit a line judge with a tennis ball Sunday.

It was a stunning end to Djokovic’s bid for an 18th Grand Slam title and his 26-0 start to this season.

Djokovic had just lost a game to his opponent, Pablo Carreno Busta, to fall behind 6-5 in the first set.

As he walked to the sideline for the changeover, Djokovic smacked a ball behind him. The ball hit a female line judge, who dropped to her knees at the back of the court.

After a discussion of several minutes with officials on court, Djokovic walked over to shake hands with Carreno Busta, and the default was announced.

While Djokovic did not speak to media as he left the court, the 33-year-old apologized to fans and players on Instagram soon after the match.

 
 
 
 
 
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This whole situation has left me really sad and empty. I checked on the lines person and the tournament told me that thank God she is feeling ok. I‘m extremely sorry to have caused her such stress. So unintended. So wrong. I’m not disclosing her name to respect her privacy. As for the disqualification, I need to go back within and work on my disappointment and turn this all into a lesson for my growth and evolution as a player and human being. I apologize to the @usopen tournament and everyone associated for my behavior. I’m very grateful to my team and family for being my rock support, and my fans for always being there with me. Thank you and I’m so sorry. Cela ova situacija me čini zaista tužnim i praznim. Proverio sam kako se oseća linijski sudija, i prema informacijama koje sam dobio, oseća se dobro, hvala Bogu. Njeno ime ne mogu da otkrijem zbog očuvanja njene privatnosti. Jako mi je žao što sam joj naneo takav stres. Nije bilo namerno. Bilo je pogrešno. Želim da ovo neprijatno iskustvo, diskvalifikaciju sa turnira, pretvorim u važnu životnu lekciju, kako bih nastavio da rastem i razvijam se kao čovek, ali i teniser. Izvinjavam se organizatorima US Opena. Veoma sam zahvalan svom timu i porodici što mi pružaju snažnu podršku, kao i mojim navijačima jer su uvek uz mene. Hvala vam i žao mi je. Bio je ovo težak dan za sve.

A post shared by Novak Djokovic (@djokernole) on

 

"This whole situation has left me really sad and empty. I checked on the lines person and the tournament told me that thank God she is feeling ok," Djokovic wrote. "I‘m extremely sorry to have caused her such stress. So unintended. So wrong. I’m not disclosing her name to respect her privacy. As for the disqualification, I need to go back within and work on my disappointment and turn this all into a lesson for my growth and evolution as a player and human being.
 
"I apologize to the @usopen tournament and everyone associated for my behavior. I’m very grateful to my team and family for being my rock support, and my fans for always being there with me. Thank you and I’m so sorry," he concluded. 
 
The tennis star will lose $250,000 in prize money as well as his current ranking points. 
 
This isn't the first time Djokovic's temper has gotten him in trouble during a match. In 2016, Djokovic hit a ball into the crowd after conceding a match the first set during a match against Dominic Thiem. 
 
Fortunately, the ball did not strike anyone in the crowd, but the tennis player was questioned for the risky move by reporters after the match. 
 
"Does it concern you one day that will cost you dearly? If it hit someone today, is that something you've got to address?" a reporter asked Djokovic at the time. But Djokovic laughed off the question, saying, "You guys are unbelievable," later adding, "It's not an issue for me."